Not a lot of info to go on here. What have you eliminated as a cause?

 

No elimination yet, what are you suggesting to me ?

Thanks in advance

 

I'm suggesting there are myriad things that could be causing the problem and you need to check your fuel delivery and ignition systems to eliminate some possible causes. For someone to make an educated guess with no history of maintenance or modifications is shooting in the dark.

EZ's shot-fuel starvation- could come from multiple issues, as could an interruption in regular ignition.

Other factors could enter into it; how long have you owned the machine, how is it stored, who maintains it and when did it start screwing up. When was the last tune-up, what was involved, who did the work.... I could go on and on.

If you asked a qualified shop mechanic the same thing, the first thing he would say is; "Don't know. Bring it in and pay me by the hour to figure it out." So the more you check out and eliminate as a cause on your own, the less time (and money) would be spent making it right. Since you're requesting some help for free here, do us a favor and do some of the checkout work yourself and if you still can't figure it out, at least we have a place to start.

 

sounds like fuel starvation
filter?
petcock screen in fuel tank?
old fuel lines can collapse on inside from today's gas
just some ideas

 

Spark plugs? Plug wires? Moisture causing a short. Fuel pump, pump relay.

 

Oops, forgot to mention starter relay

 

lol
compression good?
rings?
carbs clean?

 

Thanks guys for your suggestions
I will check filter, lines

Also, i was thinking about the fuel pump or the relay
If the pump is defect, maybe she cannot maintain the pressure for 5000 rpm or more, but it is ok for idle speed. If it is the problem it should be become worst over time.

Does the pump relay can be intermittent ?
i think it is easy to check the resistance according to manual shop for the relay.

The weird thing on this, it is the idle speed that become ok after the first big loose of power. really weird.... Maybe this point more on fuel salvation like 185EZ said and discard the pump and relay....

 

You are totally right Hammerhead


Check the fuel pump relay seems ok according to the resistance shown in the manuel shop.
Put 12 v on the fuel pump and hear it running but i do not test the pressure.
According to the last owner the fuel pump has no more than 15 000 Km.

I do not think it is a ignition problem (my opinion) because the problem is only at cruise speed. if it is an igintion problem it would be present too at idle speed (correct me if i am wrong).

It is seems to point at a starvation fuel problem
Crap in the fuel rail ??
fuel filter (have to check this one)

Thanks

 

My point was, any of the suggested ills could be responsible. I'm sure there are more. You begin by eliminating the simplest of possible causes and go on to check the more arcane possibilities. Any don't toss any money at it until you know it's necessary.

 

My point was, any of the suggested ills could be responsible. I'm sure there are more. You begin by eliminating the simplest of possible causes and go on to check the more arcane possibilities. Any don't toss any money at it until you know it's necessary.

exactly
I see so many times guys replacing fuel pumps and expensive parts before the process of elimination.
You know, simple things like a clogged gas cap vent that would create a vacuum in the tank and cause fuel starvation during heavy use and go back to normal during an idle.

 

Well Problem solve.

Remove the fuel tank and found an unplug hose coming from the air filter housing and going to the canister valve (unplug at the canister valve)

Run fine now !!

Thanks for the support to all who reply

 

Yay!
Thanks for letting us know what the problem was
ride safe